三唑类手性杀菌剂在水稻生态体系中对映体残留行为和毒性差异分析

Triazole chiral fungicides were extensively used to control of the fungal diseases on paddy production, however, they were nearly high toxic to fish and persistent in environment, even some of them are potential carcinogen, thereby; it is an hot issue for these type pesticides to the human health and environment safety. Therefore, two typical extensive used triazole chiral fungicides propiconazole and difenoconazole, were selected to study, and their single enantiomers were separated and prepared to make sure the bioactivity on target organisms and ecotoxicity. The racemate and optical pure enantiomers fungicides were simulated to be applied in paddy ecosystem and the stereoselective environmental fate of chiral pesticide in sludge, water and paddy plant were studied, to find out the main metabolites and degradation products, and to explore the major mechanisms of chiral pesticide stereoselectivity. The fate of high toxicity body and high bioactivity body of propiconazole and difenoconazole in sludge, water and paddy were revealed, to make sure the critical control points of the paddy production and environmental safety. It is helpful to provide a theoretical basis for food and environmental risk assessment of triazole chiral pesticide used in paddy production in China.

针对我国水稻生产中大量使用的三唑类手性杀菌剂，其残留分布广、降解慢，且对水生生物毒性高，甚至某些品种具有潜在致癌作用，给人类健康和环境安全带来了重大威胁。而开展对映体水平的农药残留行为和毒性差异研究是解决该问题的有效途径。本课题拟选取水稻生产中广泛使用的三唑类杀菌剂丙环唑和苯醚甲环唑为研究对象，进行手性对映体分离及手性单体制备，研究对映体对靶标生物的活性和对非靶标生物的毒性差异，明确其高效体和高毒体。在我国典型水稻生态环境下分别将供试手性农药的外消旋体和手性单体模拟施药，研究不同对映体在底泥、水和水稻中的选择性环境行为和降解规律，明确其主要降解产物和代谢途径，分析其在不同环境中代谢差异及影响因素，探讨其立体选择性机制。揭示供试手性农药高毒体和高效体的在底泥-水-水稻生态体系中的主要归趋，明确水稻生产和环境安全的关键控制点，为水稻生态系统中三唑类手性农药的环境风险评估提供基础数据和理论依据。

选择水稻常用手性杀菌剂丙环唑和苯醚甲环唑等为研究对象，采用基质分散和固相萃取相结合前处理方法，利用手性固定相和串联质谱结合技术，成功建立了丙环唑、苯醚甲环唑等手性农药残留分析方法。利用分析方法，明确了丙环唑及苯醚甲环唑手性农药对映体在水稻环境因子的对映体残留行为，发现丙环唑在水稻植株（尤其在嫩株）中存在立体选择行为，而在稻田水和土中未有明显的立体选择行为。而苯醚甲环唑对映体在水稻植株、水和土壤中均存在立体降解行为，选择强度为土壤>植株>水。生物活性和生态毒性数据表明，丙环唑对映体的活性次序因病菌而异，活性相差最高达23.47倍（水稻恶苗病），最小相差2.43倍（稻曲病）；而对水生生物活性差异不大（最高2.25倍），因此，对水稻生产不建议开发使用丙环唑单一光学纯异构体；苯醚甲环唑对水稻4种致病菌的生物活性存在差异，其中（2S,4R）-苯醚甲环唑为高活性体，（2S,4S）-苯醚甲环唑为为低活性体，相差倍数最高4.36倍（水稻立枯病）；对斜生栅藻、大型溞和斑马鱼的急性毒性均存在差异，其中（2R,4S）苯醚甲环唑对映体毒性最高，（2S,4S）苯醚甲环唑对映体毒性最低，水生毒性最高相差6.78倍（大型溞）；建议开发低含量（2S,4S）-苯醚甲环唑的农药产品，从而在源头减少农药使用量和环境风险，同时还揭示了水稻生产使用的其它手性农药的安全性，对指导手性农药的合理使用提供了重要基础数据。本项目共培养博士2名和硕士2名，共发表文章17篇，其中SCI收录16篇。